V. Enclosed Zone Load - IGNORE Specifications
Verify the load distribution of a floor with members designated not to contribute to load distribution.
Details
The three story structure is modeled with beams. The 1st and 2nd floors (above ground) include internal beams where as the 3rd floor (top) does not.
Three beams on the middle floor should be ignored for load distribution purposes.
Determine the total member load of each of the beams on the middle floor.
Validation
To match the sign output from STAAD.Pro, the global positive direction of Y is assumed for loads as well (i.e., loads acting with gravity are negative).
Members 14, 16, and 47
With the ignored beams, the tributary areas along the right side of the floor act like a "one way" floor load distribution. That is, the floor distributes load as though it were a simply supported beam span.
- The width of the tributary area: b = ½ (3 m) = 1.5 m
- The tributary area is: 6 m × 1.5 m = 9 m2
- The total member load is: -2 kN/m2 × 9 m2 = - 18 kN
Members 13 and 17
The yield line is taken as half of the angle between the beams, or 45° in this case. The tributary area given by yield line theory is a trapezoid.
- The width of the tributary area: b = ½ (6 m) = 3 m
- The average length of the tributary area: l = ½ (9 m + 3 m) = 6 m
- The tributary area is: 3 m × 6 m = 18 m2
- The total member load is: -2 kN/m2 × 18 m2 = - 36 kN
Member 18
The tributary area given by yield line theory is a triangle.
- The width of the tributary area: b = 3 m
- The tributary area is: ½ (3 m × 3 m) = 9 m2
- The total member load is: -2 kN/m2 × 9 m2 = - 18 kN
Member 50
The tributary area given by yield line theory is a triangle (sim. to member 18) and a rectangle (sim. to member 14).
- The tributary area is: 9 m2 + 9 m2 = 18 m2
- The total member load is: -2 kN/m2 × 18 m2 = - 36 kN
Note: The STAAD.Pro model contains different beam arrangements and enclosed zone
definitions for each framed floor for further comparison.
Note: The STAAD.Pro output
provides results per member at each of 16 internal analysis points along the member.
Add the internal reported loads along the member for comparison.
| Members | 13 | 14 | 16 | 17 | 18 | 47 | 50 | |
|---|---|---|---|---|---|---|---|---|
| 1 | -0.3164 | -1.1025 | -1.1025 | -0.3164 | -0.1406 | -1.1025 | -0.1406 | -1.1025 |
| 2 | -0.9492 | -1.125 | -1.125 | -0.9492 | -0.4219 | -1.125 | -0.4219 | -1.125 |
| 3 | -1.582 | -1.125 | -1.125 | -1.582 | -0.7031 | -1.125 | -0.7031 | -1.125 |
| 4 | -2.2148 | -1.125 | -1.125 | -2.2148 | -0.9844 | -1.125 | -0.9844 | -1.125 |
| 5 | -2.8477 | -1.125 | -1.125 | -2.8477 | -1.2656 | -1.125 | -1.2656 | -1.125 |
| 6 | -3.3398 | -1.125 | -1.125 | -3.3398 | -1.5469 | -1.125 | -1.5469 | -1.125 |
| 7 | -3.375 | -1.125 | -1.125 | -3.375 | -1.8281 | -1.125 | -1.8281 | -1.125 |
| 8 | -3.375 | -1.125 | -1.125 | -3.375 | -2.1094 | -1.125 | -2.1094 | -1.125 |
| 9 | -3.375 | -1.125 | -1.125 | -3.375 | -2.1094 | -1.125 | -2.1094 | -1.125 |
| 10 | -3.375 | -1.125 | -1.125 | -3.375 | -1.8281 | -1.125 | -1.8281 | -1.125 |
| 11 | -3.3398 | -1.125 | -1.125 | -3.3398 | -1.5469 | -1.125 | -1.5469 | -1.125 |
| 12 | -2.8477 | -1.125 | -1.125 | -2.8477 | -1.2656 | -1.125 | -1.2656 | -1.125 |
| 13 | -2.2148 | -1.125 | -1.125 | -2.2148 | -0.9844 | -1.125 | -0.9844 | -1.125 |
| 14 | -1.582 | -1.125 | -1.125 | -1.582 | -0.7031 | -1.125 | -0.7031 | -1.125 |
| 15 | -0.9492 | -1.125 | -1.125 | -0.9492 | -0.4219 | -1.125 | -0.4219 | -1.125 |
| 16 | -0.3164 | -1.1025 | -1.1025 | -0.3164 | -0.1406 | -1.1025 | -0.1406 | -1.1025 |
| ∑ | -35.9998 | -17.955 | -17.955 | -35.9998 | -18.0 | -17.955 | -35.955 | |
Results
| Result Type | Reference | STAAD.Pro | Difference | Comments | |
|---|---|---|---|---|---|
| Total member load (kN) | Member 13 | -36 | -35.9998 | negligible | |
| Member 14 | -18 | -17.955 | negligible | ||
| Member 16 | -18 | -17.955 | negligible | ||
| Member 17 | -36 | -35.9998 | negligible | ||
| Member 18 | -18 | -18 | none | ||
| Member 47 | -18 | -17.955 | negligible | ||
| Member 50 | -36 | -35.955 | negligible | ||
STAAD.Pro Input
The file C:\Users\Public\Public Documents\STAAD.Pro 2023\Samples \Verification Models\06 Loading\Enclosed Zone Load\Enclosed Zone Load - IGNORE Specifications.STD is typically installed with the program.
STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 27-MAR-23
END JOB INFORMATION
*Enclosed Zone example with IGNORE LOAD, IGNORE MEMBER features
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
2 0 0 12; 3 12 0 12; 4 12 0 0; 5 9 0 0; 6 9 0 6; 7 0 0 6; 8 0 4 12; 9 12 4 12;
10 12 4 0; 11 9 4 0; 12 9 4 6; 13 0 4 6; 14 0 8 12; 15 12 8 12; 16 12 8 0;
17 9 8 0; 18 9 8 6; 19 0 8 6; 20 0 12 12; 21 12 12 12; 22 12 12 0; 23 9 12 0;
24 9 12 6; 25 0 12 6; 26 12 8 6; 27 9 8 12; 28 12 4 6; 29 9 4 12;
MEMBER INCIDENCES
7 2 8; 8 3 9; 9 4 10; 10 5 11; 11 6 12; 12 7 13; 13 8 29; 14 9 28; 15 10 11;
16 11 12; 17 12 13; 18 13 8; 19 8 14; 20 9 15; 21 10 16; 22 11 17; 23 12 18;
24 13 19; 25 14 27; 26 15 26; 27 16 17; 28 17 18; 29 18 19; 30 19 14; 31 14 20;
32 15 21; 33 16 22; 34 17 23; 35 18 24; 36 19 25; 37 20 21; 38 21 22; 39 22 23;
40 23 24; 41 24 25; 42 25 20; 43 26 16; 44 18 26; 45 27 15; 46 18 27; 47 28 10;
48 12 28; 49 29 9; 50 29 12;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 2.05e+08
POISSON 0.3
DENSITY 76.8195
ALPHA 1.2e-05
DAMP 0.03
G 7.88462e+07
TYPE STEEL
STRENGTH RY 1.5 RT 1.2
END DEFINE MATERIAL
MEMBER PROPERTY AMERICAN
7 TO 50 TABLE ST W12X65
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
2 TO 7 FIXED
DEFINE ENCLOSED ZONE
ENCLOSED ZONE ZONE1
BOUNDARY 25 20 TO 24
ENCLOSED ZONE ZONE2
BOUNDARY 19 14 TO 18
IGNORE MEMBER 44
ENCLOSED ZONE ZONE3
BOUNDARY 13 8 TO 12
IGNORE LOAD 15 48 49
END
LOAD 1 LOADTYPE Dead TITLE LOAD CASE 1
ENCLOSED ZONE LOAD
ZONE1 LZ -2
LOAD 2 LOADTYPE Dead TITLE LOAD CASE 2
ENCLOSED ZONE LOAD
ZONE2 LZ -2
LOAD 3 LOADTYPE Dead TITLE LOAD CASE 3
ENCLOSED ZONE LOAD
ZONE3 LZ -2
PERFORM ANALYSIS PRINT LOAD DATA
FINISH
STAAD.Pro Output
LOADING 3 LOADTYPE DEAD TITLE LOAD CASE 3 ----------- STAAD SPACE -- PAGE NO. 8 MEMBER LOAD - UNIT KN METE MEMBER UDL L1 L2 CON L LIN1 LIN2 13 -0.3164 GY 0.38 13 -0.9492 GY 0.88 13 -1.5820 GY 1.42 13 -2.2148 GY 1.98 13 -2.8477 GY 2.54 13 -3.3398 GY 3.10 13 -3.3750 GY 3.66 13 -3.3750 GY 4.22 13 -3.3750 GY 4.78 13 -3.3750 GY 5.34 13 -3.3398 GY 5.90 13 -2.8476 GY 6.46 13 -2.2148 GY 7.02 13 -1.5820 GY 7.57 13 -0.9492 GY 8.13 13 -0.3164 GY 8.63 14 -1.1025 GY 0.19 14 -1.1250 GY 0.56 14 -1.1250 GY 0.94 14 -1.1250 GY 1.31 14 -1.1250 GY 1.69 14 -1.1250 GY 2.06 14 -1.1250 GY 2.44 14 -1.1250 GY 2.81 14 -1.1250 GY 3.19 14 -1.1250 GY 3.56 14 -1.1250 GY 3.94 14 -1.1250 GY 4.31 14 -1.1250 GY 4.69 14 -1.1250 GY 5.06 14 -1.1250 GY 5.44 14 -1.1025 GY 5.81 16 -1.1025 GY 0.19 16 -1.1250 GY 0.56 16 -1.1250 GY 0.94 16 -1.1250 GY 1.31 16 -1.1250 GY 1.69 16 -1.1250 GY 2.06 16 -1.1250 GY 2.44 16 -1.1250 GY 2.81 16 -1.1250 GY 3.19 16 -1.1250 GY 3.56 16 -1.1250 GY 3.94 16 -1.1250 GY 4.31 16 -1.1250 GY 4.69 16 -1.1250 GY 5.06 16 -1.1250 GY 5.44 16 -1.1025 GY 5.81 17 -0.3164 GY 0.38 17 -0.9492 GY 0.88 STAAD SPACE -- PAGE NO. 9 17 -1.5820 GY 1.42 17 -2.2148 GY 1.98 17 -2.8477 GY 2.54 17 -3.3398 GY 3.10 17 -3.3750 GY 3.66 17 -3.3750 GY 4.22 17 -3.3750 GY 4.78 17 -3.3750 GY 5.34 17 -3.3398 GY 5.90 17 -2.8476 GY 6.46 17 -2.2148 GY 7.02 17 -1.5820 GY 7.57 17 -0.9492 GY 8.13 17 -0.3164 GY 8.63 18 -0.1406 GY 0.25 18 -0.4219 GY 0.58 18 -0.7031 GY 0.95 18 -0.9844 GY 1.32 18 -1.2656 GY 1.69 18 -1.5469 GY 2.07 18 -1.8281 GY 2.44 18 -2.1094 GY 2.82 18 -2.1094 GY 3.18 18 -1.8281 GY 3.56 18 -1.5469 GY 3.93 18 -1.2656 GY 4.31 18 -0.9844 GY 4.68 18 -0.7031 GY 5.05 18 -0.4219 GY 5.42 18 -0.1406 GY 5.75 47 -1.1025 GY 0.19 47 -1.1250 GY 0.56 47 -1.1250 GY 0.94 47 -1.1250 GY 1.31 47 -1.1250 GY 1.69 47 -1.1250 GY 2.06 47 -1.1250 GY 2.44 47 -1.1250 GY 2.81 47 -1.1250 GY 3.19 47 -1.1250 GY 3.56 47 -1.1250 GY 3.94 47 -1.1250 GY 4.31 47 -1.1250 GY 4.69 47 -1.1250 GY 5.06 47 -1.1250 GY 5.44 47 -1.1025 GY 5.81 50 -0.1406 GY 0.25 50 -0.4219 GY 0.58 50 -0.7031 GY 0.95 50 -0.9844 GY 1.32 50 -1.2656 GY 1.69 50 -1.5469 GY 2.07 50 -1.8281 GY 2.44 50 -2.1094 GY 2.82 50 -2.1094 GY 3.18 50 -1.8281 GY 3.56 STAAD SPACE -- PAGE NO. 10 50 -1.5469 GY 3.93 50 -1.2656 GY 4.31 50 -0.9844 GY 4.68 50 -0.7031 GY 5.05 50 -0.4219 GY 5.42 50 -0.1406 GY 5.75 50 -1.1025 GY 0.19 50 -1.1250 GY 0.56 50 -1.1250 GY 0.94 50 -1.1250 GY 1.31 50 -1.1250 GY 1.69 50 -1.1250 GY 2.06 50 -1.1250 GY 2.44 50 -1.1250 GY 2.81 50 -1.1250 GY 3.19 50 -1.1250 GY 3.56 50 -1.1250 GY 3.94 50 -1.1250 GY 4.31 50 -1.1250 GY 4.69 50 -1.1250 GY 5.06 50 -1.1250 GY 5.44 50 -1.1025 GY 5.81